As a test, I did a search through 20 MB of logs I have for a locale-specific San Diego IRC channel. I found 111 uses of "tfti". The earliest I have on file dates back to February 2016.
Maybe it's not ubiquitous, but it's certainly not a unique feature of Liberal, Kansas.
First I've heard of it too. The article says "thanks for the invite" but I googled it and the top Google result says "thanks for the info", so it doesn't seem like people agree on what it means.
Are we sure people in Liberal aren't saying it ironically? Most people who pronounce Internet slang acronyms IRL are doing it ironically and the fad wears off quickly.
I'm from Liberal. I've never heard a person here (or anywhere) use the pronunciation "tifty" in any context, but I imagine you're right -- I'm sure plenty use the phrase ironically.
I've seen the initialism TFTI used in earnest, but I would consider the usage that the article refers to as uncommon at best.
Maybe it's not ubiquitous, but it's certainly not a unique feature of Liberal, Kansas.